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March Nature Almanac: Dazzling drakes challenge the icy cold

By Stephen Jones and Ruth Carol Cushman For the Camera

Posted:
02/27/2013 05:33:18 PM MST

Updated:
02/27/2013 05:34:27 PM MST

Bufflehead males and females stay close together after pairing up during winter. The male, an "attractive nuisance" when it comes to predators, will leave the female's territory as soon as she lays her eggs in a tree cavity. (Stephen Jones photo)

Other March events

Golden eagles lay their eggs in nests located high on cliff faces in the foothills and mountains.

Mountain and western bluebirds gather in flocks on the plains before moving up into the foothills to nest. Migrating snow geese fly high overhead.

American white pelicans have already returned. Twenty-five were seen on Panama Reservoir, south of Longmont, on Sunday.

Black-tailed prairie dogs are born. They come up to the surface in about four weeks and attain full size in about six months. Our prairie dogs generally produce only one litter of three to seven young.

Chorus frogs chirrup and mate in prairie wetlands.

We know that winter is ebbing in Boulder County when we see white-flanked ducks cruising along the edges of ice floes on our thawing lakes and ponds.

Some of these male goldeneyes, buffleheads and mergansers have wintered here, but most have flown up from Texas and New Mexico.

Racing northward with the thawing ice gives these ducks a chance to stake out the best breeding territories in the prairie pothole country of the Dakotas and central Canada, but it may expose them to spring blizzards and subzero temperatures. Most are already paired up, having begun courtship and mating during the depth of winter.

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The male's brilliant plumage informs potential partners that he is fit and ready to breed. During courtship, male buffleheads flash their snowy white crowns, and male goldeneyes lay their heads on their backs to expose their glistening white breasts. A study of pintail drakes found that males with the whitest breasts were most successful at attracting mates.

But conspicuous plumage attracts predators. Once the hen has laid her eggs in a nest on the ground (mergansers) or in a tree cavity (bufflehead and goldeneyes), her mate will desert her, cruising off to a quiet inlet to molt into drabber plumage and pass away the summer on his own.

This vulnerability to predators may partially explain why male diving ducks typically molt long before females do. Ducks undergo a "simultaneous wing molt," losing most of their flight feathers all at once. As a result, they're unable to fly for several weeks.

Just prior to molting, tens of millions of male ducks fly north to remote boreal forests and Arctic marshes, where they can hide from predators, including humans, during this flightless period. In early fall, male ducks undergo a second molt back into breeding plumage.

We wondered why so many of our diving ducks (ducks that forage by plunging headfirst to the bottom instead of dabbling on the surface) sport brilliant white plumage. White feathers seem like the last thing a duck would want in cold conditions, since they reflect sunlight. But perhaps the competitive advantages gained from having flashy plumage outweigh the loss of solar absorption.

To keep warm, all ducks rely on multiple layers of down, perhaps the world's best form of insulation, under their colorful outer feathers. In fact, a single duck may grow 15,000 individual feathers, and feathers alone may comprise up to 12 percent of its total body weight.

In March, look for migrating buffleheads, common goldeneyes, common mergansers, hooded mergansers and other divers at Baseline Reservoir, Sombrero Marsh, Walden Ponds and the Crane Hollow area west of Hygiene. As spring progresses, these cold-hardy divers should gradually give way to our resident dabblers, including mallards, teal and pintails.

Stephen Jones and Ruth Carol Cushman are authors of "Wild Boulder County" and the "Peterson Field Guide to the North American Prairie."

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